Gooper Blooper is a giant Blooper with large and longer tentacles. He first appears as a boss in Super Mario Sunshine, where he appears in the levels Ricco Harbor and Noki Bay. He uses his tentacles to smack Mario, draining his health. After his debut in Super Mario Sunshine and reappearance in Super Princess Peach, Gooper Blooper was reduced to a character in various sports games and spin-offs.

Gooper Blooper makes his debut in Super Mario Sunshine. While hiding under a mountain of crates, Gooper Blooper leaves one of his tentacles sticking out, and not knowing what it is, Mario pulls on the tentacle and breaks it off of Gooper Blooper's body.

Mario fighting Gooper Blooper.

Enraged, Gooper Blooper attacks using his tentacles, but each one of his tentacles is pulled off, same as the first. After washing the black ink off its face, Mario can pull the cork out of Gooper Blooper's mouth, causing ink to spray all over Gooper Blooper and the surrounding area. It is possible to beat Gooper Blooper without pulling off any tentacles, though it is very difficult, as Gooper Blooper will immediately attack if Mario grabs his cork.

With the cork gone, Mario can then pull Gooper Blooper's mouth back and let go to snap it back into his face like elastic, causing the boss severe harm. After his mouth is pulled and snapped back twice, Gooper Blooper is defeated, and he blasts off into the sky, landing in the part of the sea covered in goop.

However, Gooper Blooper survives, and is fought the same way with re-grown tentacles in Ricco Harbor, this time on the helicopter pad. When not sprayed by water during this point, Gooper Blooper spins around, hitting the player with his tentacles. Once the same tactic is used again, Gooper Blooper is blasted off into the sky and crashes into the sea.

Gooper Blooper resurfaces in Noki Bay on the peak of the mountain. Upon defeat this time, he crashes into the mountain side.

Gooper Blooper reappears in Mario Power Tennis where he is the opponent in the minigame Gooper Blooper Volley. All four of his tentacles wield a tennis racket. Here, the player attempts to hit a tennis ball between them and Gooper Blooper while avoiding the crossed-out panels. Also, at the beginning of the minigame, the tennis ball comes out of Gooper Blooper's mouth.

Gooper Blooper appears again in Super Princess Peach as the fifth Boss in the game, and is damaged by whacking his tentacles and mouth with Perry. After he loses four health points, he uses the Calm vibe to fall asleep and regain health. Princess Peach can wake him up by whacking the bubble five times and takes out his remaining two health points. He is larger in this game, compared to others.

In Mario Hoops 3-on-3, Gooper Blooper appears in the court called Pirate Ship. His task is similar to the mythical monster, the Kraken, and he surrounds the ship in a menacing way and attacks the player. Gooper Blooper smacks the player with his tentacles if the player gets too close to the edge. Due to the fact that the sky is dark and stormy and that he isn't right at the side of the boat, Gooper Blooper may be hard to notice.

Gooper Blooper appears again in Mario Super Sluggers as a hazard in the minigame Blooper Baserun, where players must dodge his tentacles and collect coins. He also appears around the Daisy Cruiser stadium at night, and grabs the ship and tilts it to its side. He seems to be bigger in this game than in the previous ones. This game is also the first game to depict Gooper Blooper swimming in water, as in his first appearance in Super Mario Sunshine, he disappeared when he touched it, though it might have to do with the fact that the Ricco Harbor's water was polluted at the time.

Gooper Blooper returns once again in Mario & Sonic at the London 2012 Olympic Games, where he is the final obstacle in the Dream Rafting competition in Cheep Cheep River. When faced, Gooper Blooper traps the competitors' raft in a whirlpool and will try to slam them with his tentacles. If the player dodges it successfully, they can use this chance to jump on his tentacles. Once all four tentacles are jumped on, Gooper Blooper will begin to quiver in pain and leap into the air, landing back down in the water defeated and dazed. A cover version of his original boss music from Super Mario Sunshine is used during the battle. This is the only game that Gooper Blooper appears in without Petey Piranha.

In battle, Gooper Blooper's attacks are determined according to the music. In the beginning, he will start off with a double slap using his front tentacles. After that, he will use his back tentacles for a considerably weaker double slap. Once the music changes again, Gooper Blooper can slap with all four of his large tentacles. Possibly to add more to the musical effect, when Gooper Blooper is performing his battle stance before he does a double slap, two of his tentacles will be raised in the air and glowing, while the other two will be clapping to the music, and in his stance for a quadruple slap, all four of his tentacles will be clapping and glowing. When the music changes once more, Gooper Blooper will turn dark purple, signifying he is about to spray Mario with poison. If Mario is hit with this attack, he will be poisoned for four turns. As well, parts of the screen will be covered in goop. Using a Leaf or blocking the poison will reduce the attack's damage to 2. Finally, when Gooper Blooper is poisoned by his own attack via the Sponge Sticker, the battle music changes into a cover of the Super Mario Bros. theme.

Gooper Blooper is a larger than average Blooper who never displays much in the way of intelligence and, like most Bloopers, can only speak in indiscernible "bloops". He appears to be loyal to the Koopa Troop, most especially his Bloopers, and will attack anyone who poses a threat to Bowser's plans or attacks his Bloopers, showing that he is also ruthless. He has even attacked ships and sports events on occasion. He also aims to destroy Mario, likely due to his interference in the Koopa Troop's plans and that he tore off one of Gooper Blooper's tentacles upon their first meeting. In Paper Mario: Sticker Star, he is revealed to actually be a music lover who loves to "boogie and bop", and spends most of his time playing music with his Bloopers.

Gooper Blooper can use all his tentacles to his advantage, whether it be slamming them all down on Mario at once or just slamming one down. Gooper Blooper will also twirl around swinging his tentacles hurting anyone who gets in their path. Gooper Blooper is also very strong, as he can tilt the entire Daisy Cruiser to one side. Like all Bloopers, Gooper Blooper can spit out ink to cause a slippery mess, and he can swim in unpolluted water as well. His ink is even capable of contaminating water on certain occasions. He can also jump very high which is shown in "Gooper Blooper Breaks Out". However, Gooper Blooper has never shown the ability, apart from in Paper Mario: Sticker Star to speak or walk on land. He has also been shown to be very adept at playing tennis, as in Mario Power Tennis, the player can continue volleying a tennis ball between themselves and Gooper Blooper virtually forever.

The culprit behind the poisoning of Wiggler's forest, even this bruiser is thinned down in Paper Mario. Really, he looks more like a dried squid... but don't let this fool you—he's still plenty dangerous. He also spits poisonous ink. Grody.

A villain who squirted poisonous ink all over the forest where Wiggler lives. Even in paper-thin form, he's quite the menace. He slaps with his many tentacles, almost like he's swatting flies, and that poisonous ink we mentioned earlier—he won't hesitate to squirt it right in Mario's face. Ew!

In a pre-release version of Super Mario Sunshine, Gooper Blooper was dark blue and spray blue. Its appearance was later changed to its current coloration for unknown reasons, possibly to make him look more like a regular Blooper.

Gooper Blooper has two different music themes in Super Mario Sunshine. In Ricco Harbor, he shares the same music as Petey Piranha, Wiggler, Eely-Mouth, and King Boo since he is the main boss of that level. In Noki Bay, he shares the same music as the Polluted Piranhas and Plungelos since he is a mini-boss in that level, with Eely-Mouth being the main boss instead.